The present invention relates to a method, and apparatus, for determining biocurrent distribution within a subject, and in particular to a technique for indirectly deriving a biocurrent distribution, particularly a biocurrent distribution in a brain.
Determination of such a biocurrent distribution is applied to some diagnoses as described in "Biomagnetic multichannel measurements in the pre-operative diagnostic evaluation of epilepsy," Electromedica 4/1989, which is incorporated herein by reference.
As for methods for estimating biocurrent distribution on the basis of distribution of living body surface potential derived by measurement, several methods have already been proposed as the method of representing biocurrent distribution by using a current dipole model and of calculating distribution of living body surface potential on the basis of the assumed current dipole.
Salu et al. assumed that the head had three concentric spheres having different conductivities and analytically calculated potentials generated on the head surface by current dipoles (IEEE Transactions on Biomedical Engineering, vol. 7, pp. 699-705, 1990).
Aoki et al. calculated the distribution of living body surface potential by using the boundary element method (Journal of Medical Electronics and Biological Engineering, 22-5, pp. 318-323, 1984). Further, Yamanishi et al. calculated the distribution of living body surface potential by using the finite element method (Journal of Medical Electronics and Biological Engineering, 18-2, pp. 126-132, 1980). These methods are effective as the approach for calculating the distribution of body surface potential in case where the distribution of conductivity in a subject body is not uniform and has an asymmetric shape. However, these methods need a lot of time.